1. Field of the Invention
The present invention pertains to a system and method for providing a therapeutic treatment to a patient, and, in particular, to a system and method in which the level of therapeutic treatment incrementally transitions between two predetermined levels by a predetermined amount over successive patient breathing cycles.
2. Description of the Related Art
It is well known to administer a therapeutic treatment to a patient in which the level of treatment being provided to the patient changes from a first level to a second level over a predetermined period of time. For example, devices exist that deliver a supply of breathing gas to the airway of patient in which the pressure level of the supply of breathing gas increases or ramps from a relatively low base pressure to a higher prescribed pressure level over a fixed or variable period of time, typically referred to as a ramp period. See, e.g., U.S. Pat. Nos. 5,239,995; Re. 35,295; U.S. Pat. Nos. 5,492,113; 5,551,418 and 5,823,187 all to Estes et al. and U.S. Pat. No. 5,117,819 to Servidio et al. Other U.S. Patents that teach automatically increasing the pressure level of air delivered to the patient over a variable period of time until the pressure reaches a preset operating level include U.S. Pat. No. 5,522,382 to Sullivan et al.
As noted above, each of these patents specifically define the ramp period, i.e., the period of time it takes to transition from the low to high pressure, as being based on a fixed or variable period of time, which is set and measured using a timer. For example, the ramp function for a conventional continuous positive airway pressure (CPAP) device is typically set to a low level of 3-5 cmH2O and gradually increases to the final prescribed value over a set period of time, which is usually between 5-45 minutes following the initiation of the CPAP therapy. Delivering a pressure at an initial low level and gradually increasing the pressure over the course of the ramp period at the beginning of the CPAP therapy allows the patient time to fall asleep at the lower, more comfortable, pressure, and, once asleep, provides the patient with the higher prescribed pressure necessary to treat the patient""s respiratory disorder, such as obstructive sleep apnea (OSA).
There are disadvantages with the above-described time-based conventional techniques for varying the treatment level, such as a pressure support therapy, provided to a patient. For example, the time-based pressure ramp is not well suited to ventilatory applications, where the patient does not need time to fall asleep, but wants some delay in reaching the final prescribed pressure level to adjust the mask and/or synchronize the ventilator to their breathing pattern. The above-described time-based system also does not automatically take into consideration the respiratory requirements of each particular patient. For example, a thirty second ramp may be a sufficient amount of time for many patients on a ventilator to make the necessary adjustments. If, however, the patient is breathing rapidly, the fixed thirty second delay may be too long a delay before providing the needed pressure support, thereby causing the patient some distress while they breathe rapidly and wait for the ventilator to reach the prescribed pressure level. Shorter time periods, on the other hand, may not provide the patient with enough time to perform the desired mask adjustments and ventilator synchronization.
It can also be appreciated that a time-based technique for setting the duration over which a therapeutic treatment varies between a low level to a high level is insensitive to the different needs of the overall patient population. For example, patients that breathe relatively fast may want increased pressure support sooner than patients that breathe at a relatively slow breathing rate. In which case, timer based techniques require the caregiver to recognize the particular nuisances of each patient and adjust the ventilator or pressure support device accordingly. This places a relatively large burden on the respiratory technician and may not maximize the comfort of the patient receiving respiratory assistance.
Accordingly, it is an object of the present invention to provide a patient treatment system that overcomes the shortcomings of conventional treatment systems. This object is achieved according to one embodiment of the present invention by providing a patient treatment system that, in its most general sense, includes a treatment system for providing a therapeutic treatment to a patient at variable treatment levels and a respiratory cycle monitoring system to detect a respiratory cycle of the patient so that the treatment system can discern the patient""s separate respiratory cycles. In addition, the treatment system includes a treatment modifying system that changes the treatment level being provided to the patient from a first predetermined treatment level to a second predetermined treatment level over a first predetermined number of respiratory cycles of the patient by adjusting an output of the treatment system a first predetermined amount over a second predetermined number of respiratory cycles of the patient.
In a preferred embodiment of the present invention, the treatment system is a system for delivering a flow of breathing gas to a patient, the respiratory cycle monitoring system is a sensor that monitors a physiological characteristic of the patient indicative of a respiratory cycle, and the treatment modifying system causes the output of the breathing gas delivering system to transition from either a first predetermined pressure or a first predetermined flow to either a second predetermined pressure or a second predetermined flow over the first predetermined number of respiratory cycles by adjusting an output of the system for delivering breathing gas by the first predetermined amount over the second predetermined number of patient respiratory cycles.
It is yet another object of the present invention to provide a method of providing a therapeutic treatment to a patient that does not suffer from the disadvantages associated with conventional treatment methods. This object is achieved by providing a method that includes providing a therapeutic treatment to a patient at variable treatment levels, detecting a respiratory cycle of the patient, and changing the treatment level from a first predetermined treatment level to a second predetermined treatment level over a first predetermined number of patient respiratory cycles by adjusting a treatment level by a first predetermined amount over a second predetermined number of respiratory cycles.
In another preferred embodiment for the method of treating a patient, the step of providing a therapeutic treatment includes delivering a flow breathing gas to a patient and the detecting step includes monitoring, via a sensor, a physiological characteristic of the patient indicative of a respiratory cycle. In addition, the step of changing the treatment level includes transitioning either a pressure or a flow of breathing gas from either a first predetermined pressure or a first predetermined flow to one of a second predetermined pressure or a second predetermined flow over the first predetermined number of respiratory cycles by adjusting either the flow or pressure of said breathing gas by the first predetermined amount over the second predetermined number of respiratory cycles.
Still another object of the present invention is to provide a system or method of treating a patient in which the gain, base pressure or base flow used to compute the pressure of breathing gas to be delivered to the patient is altered over a predetermined number of breathing cycles of the patient, thereby varying the flow or pressure support provided to the patient between two set levels.
These and other objects, features and characteristics of the present invention, as well as the methods of operation and functions of the related elements of structure and the combination of parts and economies of manufacture, will become more apparent upon consideration of the following description and the appended claims with reference to the accompanying drawings, all of which form a part of this specification, wherein like reference numerals designate corresponding parts in the various figures. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended as a definition of the limits of the invention.